ARM: dts: bcm2837-rpi-3-b: add GPIO expander

Add a description of the RPi3 GPIO expander that the VC4 firmware controls.
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Eric Anholt <eric@anholt.net>

arch/arm/boot/dts/bcm2837-rpi-3-b.dts

@@ -25,6 +25,23 @@ act {
 	};
 };
 
+&firmware {
+	expgpio: gpio {
+		compatible = "raspberrypi,firmware-gpio";
+		gpio-controller;
+		#gpio-cells = <2>;
+		gpio-line-names = "BT_ON",
+				  "WL_ON",
+				  "STATUS_LED",
+				  "LAN_RUN",
+				  "HPD_N",
+				  "CAM_GPIO0",
+				  "CAM_GPIO1",
+				  "PWR_LOW_N";
+		status = "okay";
+	};
+};
+
 /* uart0 communicates with the BT module */
 &uart0 {
 	pinctrl-names = "default";